Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium.
One difficulty faced in solid ink technology is identification and authentication of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. For example, unlike powdered or liquid marking materials, the solid form of ink sticks allows the ink sticks to be handled and loaded into a phase change ink printer without the need for a container or cartridge, as is typically required for liquid ink or powdered toner. In addition, the entire ink stick may be melted and consumed, with no need to dispose of, or recycle, any container. Eliminating the need for a container provides many advantages to the use of ink sticks. Containers or cartridges, however, may be provided with electronic tags, barcodes, etc. that may be used to identify and/or authenticate the ink contained therein. Without the use of a container, the mechanisms for authenticating or otherwise identifying the ink stick may be limited.
Provisions have been made to ensure that an ink stick is correctly loaded into the intended feed channel and to ensure that the ink stick is compatible with that printer. One provision is generally directed toward excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. An ink stick that does not have the appropriate key elements in the correct position for the particular insertion opening is excluded from insertion.
Ink sticks may be differentiated by keying features according to color as well as intended printing platform or series of printer. World markets, however, have created a situation where ink sticks may have to be differentiated, for example, by pricing, color table preferences, marketing programs, and geographic distribution in addition to color and/or intended printer model. Numerous different keying feature configurations must be incorporated into ink sticks in order to differentiate ink sticks based on color, printer model, marketing program, price point, geographic area, etc. A separate key plate or insertion opening configuration has been typically required for each different keying feature configuration incorporated into ink sticks.